12V diaphragm pump with a 60 litre tank. With everything closed the pump kicks on for about half a second every eight to ten seconds, all night, which is both annoying and clearly not free electrically. No visible drips anywhere under the sink and the floor is dry. Plumbing is push-fit throughout with a filter before the pump. Where's the leak I can't find?
Don't overlook the tap itself. A cartridge that doesn't fully seat, or a pull-out spray head with a worn seal, drips into the sink and straight down the drain where you'll never see a drop. Put a dry cup under the spout overnight.
Check the push-fit joints with a dry paper towel rather than your eyes. A leak small enough to cause this can be a few drops an hour, which evaporates before it ever pools and is completely invisible. Wrap a towel around each joint, leave it a few hours, and check for damp spots.
Found a weeping elbow behind a panel this way after two weeks of assuming my pump was faulty.
Also check the pressure switch adjustment. Some pumps have a small screw that sets the cut-in pressure, and if it's set too close to the cut-out pressure the pump hunts constantly even with no leak at all. Quarter turn at a time and test between each.
True, though I'd exhaust the leak checks first. Fiddling with that screw without understanding the system is a good way to end up with a pump that never shuts off.
Whatever the cause, put the pump on a switch by the door and get in the habit of killing it when you leave and at night. Everyone with a van plumbing horror story starts it with "the pump was on while we were out".
@drainfield_dave · 2mo ago · 3 replies
Short cycling with no visible water almost always means a tiny air or water leak on the pressure side, and the two places it hides are the pump head itself and the joints you can't see.
Diagnostic that takes five minutes: turn the pump on, let it pressurise, then turn the pump off at the switch and open nothing. Come back in ten minutes and turn a tap. If water comes out under pressure, the system held and the problem is likely the pump's internal check valve. If nothing comes out, pressure bled off somewhere and you have a real leak.
Also: fit an accumulator tank. About 30-40 for a small one, plumbed on the pressure side, and it stores enough water under pressure that the pump stops chattering on and off. It smooths the flow at the tap too. On most van builds it's the difference between a pump that's a background annoyance and one you don't think about.
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@two_stroke_tess · 2mo ago
Held pressure fine overnight with the pump off, so it's the check valve. Ordering a rebuild kit rather than a new pump.
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@parquet_pile · 2mo ago
The accumulator is worth fitting regardless. Mine cut pump run time noticeably and the tap stopped pulsing.
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